well, you might try hitting the bolts with some penetrating lubricant (pb blaster is the best, but don't overspray too much, the smell will linger in your car), just spray each bolt with a good shot of it, wait about 15-20 minutes, then smack each bolt with a hammer a few times (this helps the lubricant penetrate), then spray them again and see if that helps loosen them a little

it'll seem like you're pissing in the wind for distance, but it might loosen them up just enough

the next option is a torch, which you really don't want to use inside your car if you don't have to